Device for and method of height adjustment of seat with a drive motor

ABSTRACT

A device for height adjustment of a vehicle seat has a drive motor, transmissions having different lifting strokes and operating synchronously, one of the transmissions reaching an abutment earlier than the other of the transmissions, a housing provided for the transmissions and having abutment surfaces, and an abutment surface arranged so that at reaching a maximum position of a vehicle seat a transmission housing element abuts against the abutment surface so that a braking moment which exceeds a drive moment of the drive motor is produced.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a device for and a method ofheight adjustment of a seat by means of a drive motor.

[0002] Seats of vehicles, such as for example seats for occupants ofmotor vehicles are often provided nowadays with electrical drive motors.Based on cost considerations and also in view of on-board currentsupply, per occupant seat one drive motor has been provided, which actson two transmissions. In order to avoid tilting of the seat during itsupward and downward movements, it is important to drive bothtransmissions synchronously, to produce an adjusting movement of theseat which is perceived by the seat occupant as uniform movement.

[0003] With synchronous electric motors which drive two seat adjustingtransmissions, a play is positively produced by force transmittingelements such as couplings or transmission components, in a drive trainfrom the corresponding driven shafts of the electric motor to thecomponents which provide the vertical adjusting movement. The play isadjustable at the articulation points, or in other words in theconnection points of the drive components. The changeable speed leads todifferent lifting paths in the drives of the vertical movement of theseat. Furthermore, when different transmissions are used, which can bethe case from the reasons of the structural space and costs, then themanufacturing tolerances of the used transmissions also can lead todifferent lifting paths at the transmissions, which involves a tiltingof the seat surface during vertical adjustment of the seat.

[0004] During mounting of a vehicle seat, for example in a motorvehicle, the transmission which produces the vertical movement of theseat surface is incorporated in the extended condition. After this anadjustment of the vehicle seat downwardly is performed, until thetransmission travels with a small lifting path to its abutment position.Subsequently, the adjusting transmission for the vertical movement ofthe vehicle seat is uncoupled at the opposite side manually from thedrive motor and manually turned to its abutment position. These processsteps are complicated, both with respect to the mounting cycle and theoperational expenses. Furthermore, they represent an unavoidable errorsource during the adjustment of the vehicle seat drive. If to thecontrary, the adjustment does not occur, the drive motor further rotatesdue to the available play and the elasticity in the drive current, andthe transmission can be not further driven to its abutment position.This further drive movement can cause a lateral tilting of the seatwhich is not acceptable. The further driving of the transmission whichdoes not travel to its abutment position and moves “free” is the causefor an undesirable tilting of the seat surface.

SUMMARY OF THE INVENTION

[0005] Accordingly, it is an object of the present invention to providea device for height adjustment of a seat with a drive motor, whichavoids the disadvantages of the prior art.

[0006] In keeping with these objects and with others which will becomeapparent hereinafter, one feature of present invention resides, brieflystated, in a device for a height adjustment of a vehicle seat,comprising a drive motor; transmissions having different lifting strokesand operating synchronously, one of said transmissions reaching anabutment earlier than the other of said transmissions; housing providedfor said transmissions and having abutment surfaces; and an abutmentsurface arranged so that at reaching a maximum position of a vehicleseat a transmission housing element abuts against said abutment surfaceso that a braking moment which exceeds a drive moment of said drivemotor is produced.

[0007] When the device is designed in accordance with the presentinvention, the drive block of the drive motor upon reaching of the firstabutment position, prevents a further running of the drive motor forpreventing the further process of the further transmission which doesnot travel to its abutment, by applying a braking moment exceeding thedrive moment of the drive motor. Despite different lifting paths anddifferent adjustable play or different manufacturing tolerances of theutilized transmissions, transmissions with different lifting paths arefurther adjusted. The proposed inventive solution of the drive block ofthe drive motor which drives the vertical drive can be realized inadvantageous manner without an incorporation of additional parts. Thisleads as a whole to a lowering of the manufacturing and mounting costs,since the adjusting process, or in other words the manual uncoupling ofthe transmission with the long lifting path during the mounting of theseat, can be completely dispensed with.

[0008] With the elimination of the manually performed adjustment at thetransmission with the longer lifting path on the vertical adjustment ofthe vehicle seat, the error source is excluded, which occurs during amanually performed adjustment. The mounting of the inventive seat heightadjustment can be performed rationally and in short mounting time, sothat an automation of the mounting is possible.

[0009] In an advantageous manner the braking moment is produced exactlywhen by the reaching of the maximum position of the transmission withthe short lifting path, two surfaces abut against one another in acontact region. The contact region, at which the one end surface with afurther end surface adjustable by deformation produces the brakingmoment, is located with respect to the threaded spindle producing thevertical adjusting moment in a radius to a symmetry line of eachthreaded spindle. If a distance between the contact surface at which thebraking moment is produced and the symmetry line of the driving threadedspindle is selected sufficiently high, then the magnitude of the brakingmoment is influenced and adjusted so that the magnitude of the drivemoment of the drive motor is exceeded, with which it adjusts thetransmission with a longer lifting path traveling to its abutmentposition.

[0010] The braking moment can be, in addition to the suitabledimensioning of the radius with respect to the symmetry axis of thethreaded spindle, also influenced by the surface property of thecontacting abutment surfaces. This can be provided for increase of ahigher friction value, with coatings which have a higher frictioncoefficient. In the manufacture, it can be achieved especially simple byproviding the abutment surfaces with an increased roughness. Forobtaining the roughness over the service life of the automatic seatstroke adjustment, the abutment surfaces which have an increasedroughness can be hardened, so that it is guaranteed that the brakingmoment is always produced during the contact of the abutment surfacewith the deformable abutment surface of a housing element. With the useof roughness surfaces which can be produced in an especially simplemanner and lead to a reduction of manufacturing costs, the increase ofthe adjustment force of the fixed abutment surface and the deformedabutment surface can be advoided, so that the material loading isreduced.

[0011] In an especially advantageous manner, with the use of theinventive solution no additional components inside an adjusting drive ofa vehicle seat are needed. By forming a housing element which isavailable in the transmission housing of the transmission with a shortlifting path, such as for example the housing cover as a deformablecomponent, a deformation which is sufficient for the contact with thefixed abutment surface is reached to provide a tensioning path s duringreaching of the maximum position of a threaded spindle of the angulartransmission with a short lifting path. Thereby no additional mountingworks are needed, the mounting to the contrary is provided rationally,and an automation is possible.

[0012] The novel features which are considered as characteristic for thepresent invention are set forth in particular in the appended claims.The invention itself, however, both as to its construction and itsmethod of operation, together with additional objects and advantagesthereof, will be best understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a viewshowing one of two angulartransmission withdifferent lifting paths of a synchronously operating drive motor, whichis arranged centrally between both transmissions;

[0014]FIG. 2 is a cross-section through the transmission with a shorterlifting path together with a bearing with a bearing flange; and

[0015]FIG. 3 is an enlarged view of the contact region at the angulartransmission with the shorter lifting path, which produces a brakingmoment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]FIG. 1 shows two angular transmissions with different liftingpaths, which are driven by a synchronously driven drive motor.

[0017] The drive motor 1 which is formed as an electric motor as shownin FIG. 1 is located between two transmissions 2 and 3 which produce thevertical movement of a vehicle seat. The angular transmission 2 whichprovides a vertical adjustment is a transmission with a short path ofits threaded spindle 12. The angular transmission which is identifiedwith reference numeral 3 has a lifting path which exceeds the liftingpath of the above mentioned angular transmission 2. For synchronousdriving of the both angular transmissions 2 and 3, the drive motor 1 isprovided with two driven shafts 5 and 6. A coupling element 7 isconnected to the driven shaft 5 by a driven element 8. The couplingelement 7 drives with a multi-wedge profile 9 the angular transmissionwith the short lifting path. With this drive, a threaded spindle 12which extends downwardly from a transmission housing 14 is driven inrotation. The threaded spindle 12, in turn, is mounted on a bearingflange 4, in which a perforated plate 13 is received, as can be seenfrom FIG. 2.

[0018] The drive motor 1 which is formed as an electric motor includeson the other hand a long driven shaft 6 which acts through a drivenelement 11 with a longitudinal compensation, for example a multi-wedgeprofile or a similar element, on a coupling element 10. The couplingelement 10 at the transmission side is connected through a multi-wedgeprofile 9 with the angular transmission 3 with a higher lifting path.The threaded spindle of the angular transmission 3 is driven in rotationthrough the coupling element 10 and the drive shaft 6, and through theforce transmitting elements 11 or 9. The angular transmission,analogously to the view at the opposite angular transmission 2, isarticulated to a bearing flange. Instead of the above mentionedmulti-wedge profiles 9, 8, 11, it is possible to use other couplingelements which provide a longitudinal compensation or a longitudinalexpansion, such as for example a number of keys at the forcetransmitting locations.

[0019] A sectional view through the angular transmission with a shorterlifting path with a total support in bearing flange is shown in FIG. 2.The angular transmission 2 shown in FIG. 2 is illustrated in alongitudinal section. The spindle 12 mentioned in connection with FIG. 1is received in the transmission housing 14 of the angular transmission 2with a short lifting path. The threaded spindle 12 is formedrotation-symmetrically to its axis of symmetry 22 and embraces anexpanded threaded head region which carries an outer transmission,cooperating with an inner transmission 17 of a threaded sleeve 15. Thethreaded sleeve 15 which has a throughgoing opening with the innerthread17, is driven in its base region 18. For this purpose in the base region18 of the threaded sleeve 14, an outer tooth set 20 is provided. Theouter set 20 of the threaded sleeve 14 engages in the base region 18with a worm drive 19. The latter, on the one hand, is driven by thedriven moment of the drive motor 11 and through the coupling 7 or themulti-wedge profile connection 9.

[0020] With the self-engaging worm transmission 19 and the outer toothset 20 it is guaranteed that at reaching a vertical adjusting positionof the seat surface, or in other words a predetermined adjustingposition of the bearing flange 4, the seat remains in the adjustedposition and can not move from it unintentionally.

[0021] A transmission cover 21 is located in the lower region of thetransmission housing 14. It is deformable by a tensioning path s shownin FIG. 3 in a limited range. For this purpose, on the transmissioncover 21 at the lower side, abutments 24 are formed symmetrically to thethreaded spindle 12. When the threaded spindle 12 travels to its maximumposition, the bearing flange 14 abuts with its abutment surface 23against the lower side of the abutment 24 formed on the transmissionhousing cover 21.

[0022] A ball body 25 is received in the lower region of thetransmission spindle 12. With tensioning element 26, for example a screwor the like, the ball body 25 supported on the lower side of thetransmission spindle 12 is fixed in a longitudinal groove 27 of thetransmission spindle. Thereby the bearing flange 4 is fixedly connectedwith the transmission spindle which in turn is non rotatable, since thethreaded sleeve 14 is driven via the worm drive and is rotatably movedin turn in the transmission housing 12 of the angular transmission 2.

[0023]FIG. 3 shows an enlarged illustration of the abutment or contactregion on the transmission with a short lifting path which produces thebraking moment, on a significantly enlarged scale. As can be seen fromFIG. 3, abutments 24 are formed at the lower side of the transmissionhousing element 21 or in other words the transmission housing cover. Theabutment 24 which is located at the opposite side of the line ofsymmetry 22 of the threaded spindle 12 is not shown for the reasons ofvisibility. When the abutment surface 23 of the bearing flange 24 ismoved upwardly so that the surface 23 contacts the abutment 24 on thetransmission housing cover 21, the transmission housing cover 21 isdeformed by a tensioning angle s identified with reference numeral 30.Thereby the contact surface 32 formed on the transmission housing coverabuts against the opposite end side of the threaded sleeve 15. Thiscontact location is located preferably at a radius 28 with respect tothe axis of symmetry 22 of the threaded spindle 12. Thereby a driveblock is produced, so that the braking moment 31 which acts on thethreaded spindle 12 is greater than the drive moment of the drive motor1, which drives the oppositely located, freely traveling angulartransmission 3 with a longer lifting path. The braking moment 31 isformed by the radius 21 between the line of symmetry 22 and the contactregion of the surface 32 at the transmission housing cover 21 and theopposite end surface of the threaded sleeve 15.

[0024] A reduction of the mechanical loading of the components 15 and 21during their tensioning over the tensioning path 30 can be obtained inthat, the pre-tensioning force can be reduced by forming the threadedsleeve 15 in the region of its abutment surface as well as the valvecover 21 on its abutment surface 32 with a surface having higherfrictioncoefficient μ. Thereby with a lower pre-tensioning force, a sufficientlyhigh friction force is produced, so that the generation of the brakingmoment 31 is guaranteed and simultaneously the long-term loading duringthe tensioning of the valve cover 21 against the end surface at thethreaded sleeve 15 is considerably lowered.

[0025]FIG. 3 shows the position of the outer tooth set 20 on thethreaded sleeve 15, which in turn contains the inner thread 17,cooperating with the outer thread on the threaded head 16 of thethreaded spindle 12. The drive moment of the drive worm 19 is introducedin the region of the outer tooth set, so that by selection of a smallerradius 28, which is smaller than the radius 28 shown in FIG. 3, abraking moment 31 which exceeds the driven moment of the drive motor 1can be produced.

[0026] From the manufacturing point of view it is especially simple whenthe surfaces 32 of the housing cover 21 and the end surface 15 of thethreaded sleeve 15, in addition to a treatment with a high roughness,can be provided with friction increasing coatings. Therefore, asufficiently high friction force can be produced.

[0027] The braking moment 31 which is produced by the contact of the endsurface of the threaded sleeve 15 with the transmission housing cover 21deformed by the tensioning angle s identified with reference numeral 30,operates as a drive block of the drive motor 1, which when not blockedby the braking moment 31 can drive the opposite angular transmission 3with a higher lifting stroke further, so that it can lead to a tiltingof the vehicle seat. With the braking moment produced at reaching of themaximum position of the transmission with the shorter lifting path 2,the drive moment 1 is stopped in accordance with the proposed solution,without the use of further components and parts in an automatic seatheight adjustment of a vehicle seat. Thereby it is possible to utilizethe angular transmissions 2 and 3 which are produced in a massproduction and have different manufacturing tolerances and liftingstrokes. The location of the maximum position of the transmission 2 witha shorter lifting path determines the end of the drive movement of theangular transmission 3 which is “free” and not in its abutment position,during the height adjustment of the vehicle seat.

[0028] It will be understood that each of the elements described above,or two or more together, may also find a useful application in othertypes of constructions differing from the types described above.

[0029] While the invention has been illustrated and described asembodied in device for and method of a height adjustment of seat with adrive motor, it is not intended to be limited to the details shown,since various modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

[0030] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention.

[0031] What is claimed as new and desired to be protected by LettersPatent is set forth in the appended claims.

1. A device for height adjustment of a vehicle seat, comprising a drive motor; transmissions having different lifting strokes and operating synchronously, one of said transmissions reaching an abutment earlier than the other of said transmissions; a housing provided for said transmissions and having abutment surfaces; and an abutment surface being arranged so that at reaching a maximum position of a vehicle seat a transmission housing element abuts against said abutment surface so that a braking moment which exceeds a drive moment of said drive motor is produced.
 2. A device as defined in claim 1; and further comprising a threaded sleeve which receives a threaded spindle of one of said transmissions; and an abutment surface which is located at an end side opposite to said threaded sleeve.
 3. A device as defined in claim 2, wherein said threaded sleeve has a base region provided with force receiving location.
 4. A device as defined in claim 3, wherein said force receiving location is formed in an outer tooth set which cooperates with a worm drive.
 5. A device as defined in claim 1, wherein an abutment of said housing element against said abutment surface is performed by deformation of said housing element over a tensioning path s.
 6. A device as defined in claim 2, wherein a contact location between said abutment surface and said housing element is provided at a radius with respect to an axis of symmetry of said threaded spindle.
 7. A method of blocking a drive moment with which two transmissions are driven synchronously and produced different lifting strokes, comprising the steps of providing abutments at a housing of one of the transmission to define a maximum positions; and producing by a contact of a deformable housing element with an abutment surface a braking moment which exceeds a drive moment of a threaded spindle.
 8. A method as defined in claim 7; and further comprising deforming the housing element by abutting an abutment surface of a bearing flange against the abutment of one transmission housing.
 9. A method as defined in claim 7; and further comprising providing a contact region between surfaces which produce the braking moment at a radius r with respect to an axis of symmetry, which is selected so that the braking moment exceeds the drive moment.
 10. A method as defined in claim 7; and further comprising providing in a contact region between the surfaces which produce the braking moment, coatings which increase friction. 